1. Field of the Invention
The present invention relates to a voltage regulator.
2. Description of the Background Art
The data sheet for the voltage regulator MAX5097 from MAXIM Integrated Products Inc. describes a prior-art solution in which to switch between a first mode as a switching regulator and a second mode as a linear regulator, a part of the internal regulator components is turned off or modified in order to adapt their compensation networks to operating parameters. This has far-reaching consequences for the load behavior and/or operational stability. Additional circuit components are required for changing the compensation networks, which increases the complexity and circuit area. In addition, the load behavior (current drain) and the voltage precision of the output are limited, because the modified control loop must start up first and stabilize completely. If the switching regulator is switched, for example, to a linear regulator, the switching occurs by turning off the current feedback through the driver multiplexer, driving the output transistor, and reconfiguring the voltage control from the GM amplifier to the LDO mode amplifier. This has a significant impact on the load behavior so that the load may even need to be separated during the switching process and subsequent stabilization of the reconfiguration.
U.S. Pat. No. 6,150,798 discloses a voltage regulator. A control circuit can select between a switching regulator component and a linear regulator component according to a voltage difference between the battery voltage and output voltage.